The Plane of Earth is an elemental plane located in the Inner Sphere. It is an endless rock with many cave systems.
This plane of existence, like the others, was created in the beginning when the Great Bard sang everything into existence. It is intended as a barrier between the mortal Material Plane and the Astral Plane.
When the third Ishu ascended, he traveled beyond the stars and found himself in an endless sky where he was met with a boat made of clouds. He made his way through the Plane of Air until he found himself in a colossal ocean. On the surface was a whirlpool which led him to the bottom of the ocean. There he found a giant, solid wall of rock blocking his path. Using his newly gained power, he cracked the great wall, forming countless cave systems and became one with it. He crafted a crown from fine crystals found in the caverns. He then built a grand palace in a giant cave filled with large veins of gold, silver, and gemstones.